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What sliding potentiometer would I need to control 0-12v? and how do I wire one? Answered

I would like to control 12v DC with a sliding potentiometer. I would like the current to go from 0-12v DC, but I dont know whay resistance to get? 
I would also like to know how to wire them as I noticed the had 3 terminals, mabye ones a ground?

If you have a really good awnser you may get a patch.....yes, I am giving away loads right now

thanks

Oscar

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NachoMahmaBest Answer (author)2010-03-24

.  As its name implies, a potentiometer is designed to control voltage (see also voltage divider), not current. Rheostats are used to control voltage at high current. Potentiometers have three terminals; rheostats often have only two.
.  Using a resistor to control voltage at high current levels is inefficient and may produce enough heat to be a fire hazard. Check into a variable voltage regulator. Since I see "lights" in your keywords, you may want to investigate PWM.

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oscarthompson (author)NachoMahma2010-03-24

sorry I made a error... I was typing it up fast before I went to work...
I was looking at your awnser and I can undersatnd what you are saying but your links appear to be broken?

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NachoMahma (author)oscarthompson2010-03-24

.  Wikipedia is offline for some reason. The links should start working as soon as Wikipedia is back up and running.

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SafnilS (author)2015-04-18

hey is there anybody to help..... i need a potentiometer or rheostat to vary dc 0-12v... can u help me to the rating or ohm

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mathews (author)2010-03-24

There are normally 3 terminals, two end terminals which would be connected to + and 0v, and the center wiper terminal.

What are you going to use the voltage for? The pot will either not be able to supply enough current, or a lot of power will be wasted on it. It might be better to use a large pot (~>10k) to control a supply instead.

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oscarthompson (author)mathews2010-03-24

I am using the voltage for controling lights.. I don't mind how much power is lost. Its pluged in to the mains

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user

They'll waste as much as the lights consume. You're much better using a mains  dimmer on the transformer input..

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user

That would work but I have 4 channels which need a sliding pontentionmeter each.. which is running of the mains 

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user

So you need a dimmer per channel, B+Q will do something suitable for a few quid. A largish rheostat will cost a lot more than a dimmer !

Screwfix do single dimmers for a fiver a piece....

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user

I'm sorry but im not looking for somthing like that.. Do you know what potentionmeter i would need if I used 12V LEDS for a spotlight..

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user

The 12v LED spotlight is a complete different product....there about 5-10w

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user

Its just you had said they were 50W when you were asked....

5-10W is still an expensive pot - no change from 20 quid there. Each. 

Do it with this circuit, and it's cheaper and better for the LED too

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user

Ok.....I want to make this simple, its not a very big project......Rule out all of the spotlight idears (the ones I mentioned above). If I made my own spot light with about 20 LEDS to each light, would a product like this be sutiable

Or I could rule out the linear pot idear because this is what I have made already (the picture), and I could spend my money doing other things to improve it

Thanks for all your help

Oscar

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user

No, that pot has too much resistance, and it can't handle the power. My circuit costs about 2 quid per channel.

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user

How is the voltage adjusted though?

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user

It isn't directly, this thing controls the CURRENT very accurately, which gives you  the same effect.

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user

I'm not getting this? Is there any physical controling of it? what affect do they give?

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Physically controlling what ? The current ? Yes, the circuit keeps it at the constant level set by the pot in the circuit. It does THAT by controlling the voltage across the 0R5 and keeping it constant.

Steve

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user

how do you dim the lights?

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ok! now I get it now... thanks

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NachoMahma (author)oscarthompson2010-03-25

.  If you are trying to run 10W of lights, you will need a pot rated for at least 10W. If you are running 50W of lights, you will need a 50W pot. ...
.  You are not likely to find a slide pot rated for over one-half Watt (0.1W seems to be pretty "standard") and if you do it will be very expensive and generate a lot of heat when the lights are dimmed.
.
.  If you are running LEDs, you can find formulae/forms to calculate the value of current limiting resistors. Use this figure as the minimum value for your pot. Make sure your pot can candle the power.

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jeff-o (author)oscarthompson2010-03-24

While you can easily connect a potentiometer to act as a voltage divider, I do not suggest it.  Potentiometers can usually only handle about 1/4 watt, and I suspect your lights will draw more than that.  If you just use a pot, it'll evaporate in a puff of magic smoke within seconds.

What wattage are the spot lights?

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jeff-o (author)oscarthompson2010-03-24

Ha, yup, *POOF*

You'll need a purpose-made dimmer for those lights.  Take a trip to a hardware store, they'll likely have what you need in the electrical or lighting section.

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Re-design (author)2010-03-24

You need to start with something like this.  You can sub a potentiometer for one of the fixed resistors and you'll have a basic variable power supply with no frills.

Since I don't know what you're really doing with this I can't guarantee that it will work for your real purpose but this does answer your question.

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oscarthompson (author)Re-design2010-03-24

the purpose is to control spotlights

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steveastrouk (author)2010-03-24

"volts" are not "current" what are you aiming to do ? Control the current in a hot wire or something ? 

If you really mean "adjust the voltage across my load from 0..12V" then we need to know the resistance of the load.

Steve

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sorry I made a error... I was typing it up fast before I went to work...
I am aiming to control spotlights.

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RavingMadStudios (author)2010-03-24

A copper rod, a copper plate, and a barrel of seawater is all you need.

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